Optimizes SampleExpr to remove unnecessary line_format.

[cyriltovena]

When doing count_over_time and rate(), it doesn't make sense to have a line_format since you're counting line, you don't really care about what the line contains.

At the same time this set the foundation of for further optimization, like parsing only required labels during label parsing.

I've also found a bug where topk by(foo) (1... where not correctly parsed.

Signed-off-by: Cyril Tovena [email protected]

[cyriltovena]

I think it's actually for all range vector operation, will make a change to support them all

[codecov-io]

Codecov Report

Merging #3065 (5a874a4) into master (3f99a07) will increase coverage by 0.02%.
The diff coverage is 87.69%.

@@            Coverage Diff             @@
##           master    #3065      +/-   ##
==========================================
+ Coverage   62.88%   62.91%   +0.02%     
==========================================
  Files         186      187       +1     
  Lines       15949    16014      +65     
==========================================
+ Hits        10030    10075      +45     
- Misses       4987     5007      +20     
  Partials      932      932              

Impacted Files	Coverage Δ
pkg/logql/engine.go	86.16% <33.33%> (-1.02%)	⬇️
pkg/logql/optimize.go	90.32% <90.32%> (ø)
pkg/promtail/positions/positions.go	46.80% <0.00%> (-11.71%)	⬇️
pkg/ingester/checkpoint.go	67.40% <0.00%> (-0.89%)	⬇️
pkg/canary/comparator/comparator.go	77.72% <0.00%> (-0.46%)	⬇️
pkg/querier/queryrange/limits.go	95.83% <0.00%> (+4.16%)	⬆️

[owen-d]

nit then lgtm

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 87.69231% with 8 lines in your changes missing coverage. Please review.

Project coverage is 63.03%. Comparing base (3f99a07) to head (b937cae).

Files with missing lines	Patch %	Lines
pkg/logql/optimize.go	90.32%	5 Missing and 1 partial ⚠️
pkg/logql/engine.go	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3065      +/-   ##
==========================================
+ Coverage   62.88%   63.03%   +0.14%     
==========================================
  Files         186      187       +1     
  Lines       15949    16014      +65     
==========================================
+ Hits        10030    10094      +64     
- Misses       4987     4989       +2     
+ Partials      932      931       -1     

Files with missing lines	Coverage Δ
pkg/logql/engine.go	86.16% <33.33%> (-1.02%)	⬇️
pkg/logql/optimize.go	90.32% <90.32%> (ø)

... and 3 files with indirect coverage changes